The flavor combination of chocolate, coffee, and sugar in this cake is simply addicting. I love how you can take something simple like an angel food cake mix and make it spectacular with just a few added ingredients.
Preheat oven to 350°F. Move oven rack to lowest position if you're using a tube pan, or the middle position for loaf pans.
Mix cake mix with cocoa in large glass or metal bowl at low speed until blended.
Pour in coffee and mix at low speed until moistened. Then beat exactly 1 minute at medium speed. Pour batter into an ungreased tube pan (10x4-inch) or two (9x5-inch loaf pans).
Bake 35 to 45 minutes for tube pan, and 33 to 43 minutes for loaf pans. Cake is done when crust is deep golden brown and cracks on top appear dry. DO NOT UNDERBAKE.
Cool tube cake upside down on a glass bottle or heatproof surface until completely cool. Cool loaves in pans tipped on side on cooling rack until completely cool.
Loosen edges with flat knife or metal spatula to remove from pans.
Whip up whipped cream if desired, adding powdered sugar to taste toward end of whipping.